package top.abrsm.util;

import com.alibaba.fastjson.JSONObject;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.util.encoders.Base64;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.NoSuchPaddingException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import java.io.UnsupportedEncodingException;
import java.security.*;
import java.security.spec.InvalidParameterSpecException;
import java.util.Arrays;


/**
 * 解析小程序中获取的手机号码
 * 利用AES加密方式解析微信小程序中返回的数据
 * 用于小程序中获取手机号功能
 */
public class WxChatUtil {

    private static final String KEY_ALGORITHM = "AES";
    private static final String ALGORITHM_STR = "AES/CBC/PKCS7Padding";
    private static Key key;
    private static Cipher cipher;

    public static String decryptData ( String encryptDataB64, String sessionKeyB64, String ivB64 ) {
        return new String (
                decryptOfDiyIV (
                        Base64.decode ( encryptDataB64 ),
                        Base64.decode ( sessionKeyB64 ),
                        Base64.decode ( ivB64 )
                )
        );
    }

    private static void init ( byte[] keyBytes ) {
        // 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
        int base = 16;
        if ( keyBytes.length % base != 0 ) {
            int groups = keyBytes.length / base + ( keyBytes.length % base != 0 ? 1 : 0 );
            byte[] temp = new byte[groups * base];
            Arrays.fill ( temp, ( byte ) 0 );
            System.arraycopy ( keyBytes, 0, temp, 0, keyBytes.length );
            keyBytes = temp;
        }
        // 初始化
        Security.addProvider ( new BouncyCastleProvider () );
        // 转化成JAVA的密钥格式
        key = new SecretKeySpec ( keyBytes, KEY_ALGORITHM );
        try {
            // 初始化cipher
            cipher = Cipher.getInstance ( ALGORITHM_STR, "BC" );
        } catch ( Exception e ) {
            e.printStackTrace ();
        }
    }

    /**
     * 解密方法
     *
     * @param encryptedData 要解密的字符串
     * @param keyBytes      解密密钥
     * @param ivs           自定义对称解密算法初始向量 iv
     * @return 解密后的字节数组
     */
    private static byte[] decryptOfDiyIV ( byte[] encryptedData, byte[] keyBytes, byte[] ivs ) {
        byte[] encryptedText = null;
        init ( keyBytes );
        try {
            cipher.init ( Cipher.DECRYPT_MODE, key, new IvParameterSpec ( ivs ) );
            encryptedText = cipher.doFinal ( encryptedData );
        } catch ( Exception e ) {
            e.printStackTrace ();
        }
        return encryptedText;
    }

    /**
     * 获取信息
     */
    public static JSONObject getUserInfo ( String encryptedData, String sessionkey, String iv ) {
        // 被加密的数据
        byte[] dataByte = Base64.decode ( encryptedData );
        // 加密秘钥
        byte[] keyByte = Base64.decode ( sessionkey );
        // 偏移量
        byte[] ivByte = Base64.decode ( iv );
        try {
            // 如果密钥不足16位，那么就补足.  这个if 中的内容很重要
            int base = 16;
            if ( keyByte.length % base != 0 ) {
                int groups = keyByte.length / base + ( keyByte.length % base != 0 ? 1 : 0 );
                byte[] temp = new byte[groups * base];
                Arrays.fill ( temp, ( byte ) 0 );
                System.arraycopy ( keyByte, 0, temp, 0, keyByte.length );
                keyByte = temp;
            }
            // 初始化
            Security.addProvider ( new BouncyCastleProvider () );
            Cipher cipher = Cipher.getInstance ( "AES/CBC/PKCS7Padding", "BC" );
            SecretKeySpec spec = new SecretKeySpec ( keyByte, "AES" );
            AlgorithmParameters parameters = AlgorithmParameters.getInstance ( "AES" );
            parameters.init ( new IvParameterSpec ( ivByte ) );
            cipher.init ( Cipher.DECRYPT_MODE, spec, parameters );// 初始化
            byte[] resultByte = cipher.doFinal ( dataByte );
            if ( null != resultByte && resultByte.length > 0 ) {
                String result = new String ( resultByte, "UTF-8" );
                return JSONObject.parseObject ( result );
            }
        } catch ( NoSuchAlgorithmException e ) {
            e.printStackTrace ();
        } catch ( NoSuchPaddingException e ) {
            e.printStackTrace ();
        } catch ( InvalidParameterSpecException e ) {
            e.printStackTrace ();
        } catch ( IllegalBlockSizeException e ) {
            e.printStackTrace ();
        } catch ( BadPaddingException e ) {
            e.printStackTrace ();
        } catch ( UnsupportedEncodingException e ) {
            e.printStackTrace ();
        } catch ( InvalidKeyException e ) {
            e.printStackTrace ();
        } catch ( InvalidAlgorithmParameterException e ) {
            e.printStackTrace ();
        } catch ( NoSuchProviderException e ) {
            e.printStackTrace ();
        }
        return null;
    }

}
